2. Field of the Invention
The present invention relates to an exposure calculation apparatus used in an AE camera.
2. Related Background Art
As a conventional exposure calculation method, a method disclosed in, e.g., Japanese Laid-Open Patent Application No. 1-231034, is known. This method will be described below with reference to FIG. 1. An L-shaped region 2 including three corner portions of a photographing frame (objective field) 1 is cut (excluded) from the frame 1. Two L-shaped regions can be set for the photographing frame 1. Of these regions, a brighter one is cut. Similarly, a brighter L-shaped region 4 is cut from the remaining region 3, and thereafter, such processing is repeated. Thus, the remaining rectangular region becomes gradually small in size, and the darkest region 7 remains finally. An exposure value is calculated on the basis of the brightness of the darkest region 7.
In a general outdoor photographing scene, it is considered that the principal object is relatively dark, and the background (e.g., sky) is bright. Therefore, with the above-mentioned processing, a rough position of the principal object is assumed, a portion corresponding to the sky is excluded, and an exposure value is determined based only on the brightness of the principal object. In this manner, the possibility of obtaining a proper exposure value for the principal object can be increased.
In the conventional method, however, the finally remaining region 7 always becomes rectangular, while the principal object is not always rectangular. Therefore, an exposure value cannot always be accurately calculated based on the brightness of the principal object. As a result, an improper exposure value may often be obtained. When the principal object exists across sunny and shaded places, an exposure calculation is performed while cutting a portion corresponding to the sunny place, and an improper exposure value may be obtained in the same manner as described above.